/*
 * Copyright (c) 2013. wyouflf (wyouflf@gmail.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.dongfang.net.http.client.util;

import java.net.URI;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;

import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicHeaderValueParser;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.message.ParserCursor;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.CharArrayBuffer;

import android.text.TextUtils;

/**
 * A collection of utilities for encoding URLs.
 * 
 * @since 4.0
 */
public class URLEncodedUtils {

	public static final String CONTENT_TYPE = "application/x-www-form-urlencoded";
	private static final String PARAMETER_SEPARATOR = "&";
	private static final String NAME_VALUE_SEPARATOR = "=";

	/**
	 * Returns a list of {@link org.apache.http.NameValuePair NameValuePairs} as built from the URI's query portion. For
	 * example, a URI of http://example.org/path/to/file?a=1&b=2&c=3 would return a list of three NameValuePairs, one
	 * for a=1, one for b=2, and one for c=3.
	 * <p/>
	 * This is typically useful while parsing an HTTP PUT.
	 * 
	 * @param uri
	 *            uri to parse
	 * @param encoding
	 *            encoding to use while parsing the query
	 */
	public static List<NameValuePair> parse(final URI uri, final String encoding) {
		final String query = uri.getRawQuery();
		if (!TextUtils.isEmpty(query)) {
			List<NameValuePair> result = new ArrayList<NameValuePair>();
			Scanner scanner = new Scanner(query);
			parse(result, scanner, encoding);
			return result;
		}
		else {
			return Collections.emptyList();
		}
	}

	/**
	 * Returns true if the entity's Content-Type header is <code>application/x-www-form-urlencoded</code>.
	 */
	public static boolean isEncoded(final HttpEntity entity) {
		Header h = entity.getContentType();
		if (h != null) {
			HeaderElement[] elems = h.getElements();
			if (elems.length > 0) {
				String contentType = elems[0].getName();
				return contentType.equalsIgnoreCase(CONTENT_TYPE);
			}
			else {
				return false;
			}
		}
		else {
			return false;
		}
	}

	/**
	 * Adds all parameters within the Scanner to the list of <code>parameters</code>, as encoded by
	 * <code>encoding</code>. For example, a scanner containing the string <code>a=1&b=2&c=3</code> would add the
	 * {@link org.apache.http.NameValuePair NameValuePairs} a=1, b=2, and c=3 to the list of parameters.
	 * 
	 * @param parameters
	 *            List to add parameters to.
	 * @param scanner
	 *            Input that contains the parameters to parse.
	 * @param charset
	 *            Encoding to use when decoding the parameters.
	 */
	public static void parse(final List<NameValuePair> parameters, final Scanner scanner, final String charset) {
		scanner.useDelimiter(PARAMETER_SEPARATOR);
		while (scanner.hasNext()) {
			String name = null;
			String value = null;
			String token = scanner.next();
			int i = token.indexOf(NAME_VALUE_SEPARATOR);
			if (i != -1) {
				name = decodeFormFields(token.substring(0, i).trim(), charset);
				value = decodeFormFields(token.substring(i + 1).trim(), charset);
			}
			else {
				name = decodeFormFields(token.trim(), charset);
			}
			parameters.add(new BasicNameValuePair(name, value));
		}
	}

	private static final char[] DELIM = new char[] { '&' };

	/**
	 * Returns a list of {@link org.apache.http.NameValuePair NameValuePairs} as parsed from the given string using the
	 * given character encoding.
	 * 
	 * @param s
	 *            text to parse.
	 * @param charset
	 *            Encoding to use when decoding the parameters.
	 * @since 4.2
	 */
	public static List<NameValuePair> parse(final String s, final Charset charset) {
		if (s == null) {
			return Collections.emptyList();
		}
		BasicHeaderValueParser parser = BasicHeaderValueParser.DEFAULT;
		CharArrayBuffer buffer = new CharArrayBuffer(s.length());
		buffer.append(s);
		ParserCursor cursor = new ParserCursor(0, buffer.length());
		List<NameValuePair> list = new ArrayList<NameValuePair>();
		while (!cursor.atEnd()) {
			NameValuePair nvp = parser.parseNameValuePair(buffer, cursor, DELIM);
			if (nvp.getName().length() > 0) {
				list.add(new BasicNameValuePair(decodeFormFields(nvp.getName(), charset), decodeFormFields(
						nvp.getValue(), charset)));
			}
		}
		return list;
	}

	/**
	 * Returns a String that is suitable for use as an <code>application/x-www-form-urlencoded</code> list of parameters
	 * in an HTTP PUT or HTTP POST.
	 * 
	 * @param parameters
	 *            The parameters to include.
	 * @param charset
	 *            The encoding to use.
	 */
	public static String format(final List<? extends NameValuePair> parameters, final String charset) {
		final StringBuilder result = new StringBuilder();
		for (final NameValuePair parameter : parameters) {
			final String encodedName = encodeFormFields(parameter.getName(), charset);
			final String encodedValue = encodeFormFields(parameter.getValue(), charset);
			if (result.length() > 0) {
				result.append(PARAMETER_SEPARATOR);
			}
			result.append(encodedName);
			if (encodedValue != null) {
				result.append(NAME_VALUE_SEPARATOR);
				result.append(encodedValue);
			}
		}
		return result.toString();
	}

	/**
	 * Returns a String that is suitable for use as an <code>application/x-www-form-urlencoded</code> list of parameters
	 * in an HTTP PUT or HTTP POST.
	 * 
	 * @param parameters
	 *            The parameters to include.
	 * @param charset
	 *            The encoding to use.
	 * @since 4.2
	 */
	public static String format(final Iterable<? extends NameValuePair> parameters, final Charset charset) {
		final StringBuilder result = new StringBuilder();
		for (final NameValuePair parameter : parameters) {
			final String encodedName = encodeFormFields(parameter.getName(), charset);
			final String encodedValue = encodeFormFields(parameter.getValue(), charset);
			if (result.length() > 0) {
				result.append(PARAMETER_SEPARATOR);
			}
			result.append(encodedName);
			if (encodedValue != null) {
				result.append(NAME_VALUE_SEPARATOR);
				result.append(encodedValue);
			}
		}
		return result.toString();
	}

	/**
	 * Unreserved characters, i.e. alphanumeric, plus: {@code _ - ! . ~ ' ( ) *}
	 * <p/>
	 * This list is the same as the {@code unreserved} list in <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC
	 * 2396</a>
	 */
	private static final BitSet UNRESERVED = new BitSet(256);
	/**
	 * Punctuation characters: , ; : $ & + =
	 * <p/>
	 * These are the additional characters allowed by userinfo.
	 */
	private static final BitSet PUNCT = new BitSet(256);
	/**
	 * Characters which are safe to use in userinfo, i.e. {@link #UNRESERVED} plus {@link #PUNCT}uation
	 */
	private static final BitSet USERINFO = new BitSet(256);
	/**
	 * Characters which are safe to use in a path, i.e. {@link #UNRESERVED} plus {@link #PUNCT}uation plus / @
	 */
	private static final BitSet PATHSAFE = new BitSet(256);
	/**
	 * Characters which are safe to use in a fragment, i.e. {@link #RESERVED} plus {@link #UNRESERVED}
	 */
	private static final BitSet FRAGMENT = new BitSet(256);

	/**
	 * Reserved characters, i.e. {@code ;/?:@&=+$,[]}
	 * <p/>
	 * This list is the same as the {@code reserved} list in <a href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>
	 * as augmented by <a href="http://www.ietf.org/rfc/rfc2732.txt">RFC 2732</a>
	 */
	private static final BitSet RESERVED = new BitSet(256);

	/**
	 * Safe characters for x-www-form-urlencoded data, as per java.net.URLEncoder and browser behaviour, i.e.
	 * alphanumeric plus {@code "-", "_", ".", "*"}
	 */
	private static final BitSet URLENCODER = new BitSet(256);

	static {
		// unreserved chars
		// alpha characters
		for (int i = 'a'; i <= 'z'; i++) {
			UNRESERVED.set(i);
		}
		for (int i = 'A'; i <= 'Z'; i++) {
			UNRESERVED.set(i);
		}
		// numeric characters
		for (int i = '0'; i <= '9'; i++) {
			UNRESERVED.set(i);
		}
		UNRESERVED.set('_'); // these are the charactes of the "mark" list
		UNRESERVED.set('-');
		UNRESERVED.set('.');
		UNRESERVED.set('*');
		URLENCODER.or(UNRESERVED); // skip remaining unreserved characters
		UNRESERVED.set('!');
		UNRESERVED.set('~');
		UNRESERVED.set('\'');
		UNRESERVED.set('(');
		UNRESERVED.set(')');
		// punct chars
		PUNCT.set(',');
		PUNCT.set(';');
		PUNCT.set(':');
		PUNCT.set('$');
		PUNCT.set('&');
		PUNCT.set('+');
		PUNCT.set('=');
		// Safe for userinfo
		USERINFO.or(UNRESERVED);
		USERINFO.or(PUNCT);

		// URL path safe
		PATHSAFE.or(UNRESERVED);
		PATHSAFE.set('/'); // segment separator
		PATHSAFE.set(';'); // param separator
		PATHSAFE.set(':'); // rest as per list in 2396, i.e. : @ & = + $ ,
		PATHSAFE.set('@');
		PATHSAFE.set('&');
		PATHSAFE.set('=');
		PATHSAFE.set('+');
		PATHSAFE.set('$');
		PATHSAFE.set(',');

		RESERVED.set(';');
		RESERVED.set('/');
		RESERVED.set('?');
		RESERVED.set(':');
		RESERVED.set('@');
		RESERVED.set('&');
		RESERVED.set('=');
		RESERVED.set('+');
		RESERVED.set('$');
		RESERVED.set(',');
		RESERVED.set('['); // added by RFC 2732
		RESERVED.set(']'); // added by RFC 2732

		FRAGMENT.or(RESERVED);
		FRAGMENT.or(UNRESERVED);
	}

	private static final int RADIX = 16;

	private static String urlencode(final String content, final Charset charset, final BitSet safechars,
			final boolean blankAsPlus) {
		if (content == null) {
			return null;
		}
		StringBuilder buf = new StringBuilder();
		ByteBuffer bb = charset.encode(content);
		while (bb.hasRemaining()) {
			int b = bb.get() & 0xff;
			if (safechars.get(b)) {
				buf.append((char) b);
			}
			else if (blankAsPlus && b == ' ') {
				buf.append('+');
			}
			else {
				buf.append("%");
				char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, RADIX));
				char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, RADIX));
				buf.append(hex1);
				buf.append(hex2);
			}
		}
		return buf.toString();
	}

	/**
	 * Decode/unescape a portion of a URL, to use with the query part ensure {@code plusAsBlank} is true.
	 * 
	 * @param content
	 *            the portion to decode
	 * @param charset
	 *            the charset to use
	 * @param plusAsBlank
	 *            if {@code true}, then convert '+' to space (e.g. for www-url-form-encoded content), otherwise leave as
	 *            is.
	 * @return encoded string
	 */
	private static String urldecode(final String content, final Charset charset, final boolean plusAsBlank) {
		if (content == null) {
			return null;
		}
		ByteBuffer bb = ByteBuffer.allocate(content.length());
		CharBuffer cb = CharBuffer.wrap(content);
		while (cb.hasRemaining()) {
			char c = cb.get();
			if (c == '%' && cb.remaining() >= 2) {
				char uc = cb.get();
				char lc = cb.get();
				int u = Character.digit(uc, 16);
				int l = Character.digit(lc, 16);
				if (u != -1 && l != -1) {
					bb.put((byte) ((u << 4) + l));
				}
				else {
					bb.put((byte) '%');
					bb.put((byte) uc);
					bb.put((byte) lc);
				}
			}
			else if (plusAsBlank && c == '+') {
				bb.put((byte) ' ');
			}
			else {
				bb.put((byte) c);
			}
		}
		bb.flip();
		return charset.decode(bb).toString();
	}

	/**
	 * Decode/unescape www-url-form-encoded content.
	 * 
	 * @param content
	 *            the content to decode, will decode '+' as space
	 * @param charset
	 *            the charset to use
	 * @return encoded string
	 */
	private static String decodeFormFields(final String content, final String charset) {
		if (content == null) {
			return null;
		}
		return urldecode(content, charset != null ? Charset.forName(charset) : Charset.forName(HTTP.UTF_8), true);
	}

	/**
	 * Decode/unescape www-url-form-encoded content.
	 * 
	 * @param content
	 *            the content to decode, will decode '+' as space
	 * @param charset
	 *            the charset to use
	 * @return encoded string
	 */
	private static String decodeFormFields(final String content, final Charset charset) {
		if (content == null) {
			return null;
		}
		return urldecode(content, charset != null ? charset : Charset.forName(HTTP.UTF_8), true);
	}

	/**
	 * Encode/escape www-url-form-encoded content.
	 * <p/>
	 * Uses the {@link #URLENCODER} set of characters, rather than the set; this is for compatibilty with previous
	 * releases, URLEncoder.encode() and most browsers.
	 * 
	 * @param content
	 *            the content to encode, will convert space to '+'
	 * @param charset
	 *            the charset to use
	 * @return encoded string
	 */
	private static String encodeFormFields(final String content, final String charset) {
		if (content == null) {
			return null;
		}
		return urlencode(content, charset != null ? Charset.forName(charset) : Charset.forName(HTTP.UTF_8), URLENCODER,
				true);
	}

	/**
	 * Encode/escape www-url-form-encoded content.
	 * <p/>
	 * Uses the {@link #URLENCODER} set of characters, rather than the set; this is for compatibilty with previous
	 * releases, URLEncoder.encode() and most browsers.
	 * 
	 * @param content
	 *            the content to encode, will convert space to '+'
	 * @param charset
	 *            the charset to use
	 * @return encoded string
	 */
	private static String encodeFormFields(final String content, final Charset charset) {
		if (content == null) {
			return null;
		}
		return urlencode(content, charset != null ? charset : Charset.forName(HTTP.UTF_8), URLENCODER, true);
	}

	/**
	 * Encode a String using the {@link #USERINFO} set of characters.
	 * <p/>
	 * Used by URIBuilder to encode the userinfo segment.
	 * 
	 * @param content
	 *            the string to encode, does not convert space to '+'
	 * @param charset
	 *            the charset to use
	 * @return the encoded string
	 */
	static String encUserInfo(final String content, final Charset charset) {
		return urlencode(content, charset, USERINFO, false);
	}

	/**
	 * Encode a String using the {@link #FRAGMENT} set of characters.
	 * <p/>
	 * Used by URIBuilder to encode the userinfo segment.
	 * 
	 * @param content
	 *            the string to encode, does not convert space to '+'
	 * @param charset
	 *            the charset to use
	 * @return the encoded string
	 */
	static String encFragment(final String content, final Charset charset) {
		return urlencode(content, charset, FRAGMENT, false);
	}

	/**
	 * Encode a String using the {@link #PATHSAFE} set of characters.
	 * <p/>
	 * Used by URIBuilder to encode path segments.
	 * 
	 * @param content
	 *            the string to encode, does not convert space to '+'
	 * @param charset
	 *            the charset to use
	 * @return the encoded string
	 */
	static String encPath(final String content, final Charset charset) {
		return urlencode(content, charset, PATHSAFE, false);
	}

}
